Self-regulating hydraulic system



'Oct. 25, 1932. I I s' ssgfl 1,884,277

55L? REGULATING HYDRAQLIC SYSTBI I Filed April 8, 1930 's Sheets-Sheet 1 Oct. 25, 1932. i a. sAssEN SELF REGULATING HYDRAULIC SYS'IEI Filed April 8. 1930 3 Sheets-Sheet 2 0d. 25, 1932.- BQSASSEN 1,884,277

' Sm REGULATING mwnwmc sYs'rEI Filed April 8 1930 v 5 Sheets-Sheet a I i /5 V l E v E anumtoz I Patented Oct. 25, 1932 STATES PATENT OFFICE BERNARD SASSEN, OI CINCINNATI, OHIO,

MACHINE COMPANY, 01 CINCINNATI,

ASSIGNOR TO THE CINCINNATI KILLING OHIO, A CORPORATION OF OHIO SELI-BEGUIIA'IING HYDRAULIC SYSTEM This invention seeks to shoot an improvement in the common or more usual type of hydraulic transmission which,,it will be remembered, conventionally employs a variahie-delivery pump arranged to propel a motor by supplying, through a regulated forward-pressure line, a predetermined flow. The out-take from the motor is, in this conventional system, free or substantially so. Consequently this system is unadapted for any usage which requires the motorto act as a brake for regulating the rate caused by a negative work-resistance; as in cutting with the feed in a milling machine.

It is now proposed to overcome this ob ection by means for automatically maintaining a regulated back-pressure inthe out take line "from the motor; returning the out-flow from this means at a lowressure directly to the reservoir, if desired, but preferably at a low constant pressure to the in-take of the variahie-delivery pump.

While the present system, embodiments, maintains the system full of oil at all times, regardless of the in-flux and out-flux necessitated if a motor of the differential type be used, it also lends itself to a compensation for leakage which otherwise would afiect the feed rate, and how this may be accomplished will be explained later.

Other objects and advantages will be in part indicated in the following description and in part rendered apparent therefrom in connection with the annexed drawings.

To enable others skilled in the art so fully to apprehend the underlying features hereof that they may embody the same in the various ways contemplated by this invention, drawmgs depicting a preferred typical construction have been-annexed as a part of this disclosure and, in such drawings, like characters of reference denote corresponding parts throughout all the views, of which Figure 1 diagrammatically represents an embodiment of the more elementary principle underlying this invention. Fig. 2 diagrammatically discloses an improved form of this invention; while, Fig. 3 diagrammatic'ally sets forth how this invention may be embodied to ensure a feed rate unafiected by in each of itsany incidental leakage and, additionally, to.

render available a high pressure take-off line for service in actuating any device or instrumentality auxiliary to the main machine.

It is to be understood that this system finds its practical application in various types of machine-tools; but more especially in milling-machines and these diagrams are to be interpreted accordingly. Thus, T is the machine-element propelled hydraulically by the motor M*,'and V V represents the valve-means for appropriately arresting or directing the flow to and from the motor to obtain all such motions of the machine-element as have heretofore been automatically produced by mechanical means; such, for ex-v ample, as a rapid-traverse during a noncutting shift, or' a feed durin' a tooling movement; singly or combined 111 the-various cycles (involving either forward or return movements or both) conventional with machine-tool practise. Inasmuch as the dogs and trips already developed in purel me.- chanical machines are readily availa le to engineers, and likewise as to the organization of the valve-means, it is deemed unnecessary to describe such in detail; for to do so would tend to obscure rather than a disclosure of the salient characterisreference will, however, be made to the British Patent No. 297,104 which very fully shows valve and trip means such as is herein indicated diagrammatically by VV,

as well as other, details of a complete machine.

It will suflice. to say, before dwelling on the distinguishing features of this invention,

that the work-table T, will beconnected to the motor by some sort of mechanical drive indicated by the arm 15 and piston-rod '14 which enters the cylinder 12 and is attached to the piston 13. The 15 pe of the motor M is not of the essence 0 this invention, and hence is herein shown in the form most practicable and inexpensive for most installations; to wit, as a differential piston-and-. cylinder motor.

Its ports are indicated by a: and 'y; the one being the inlet and the other the outlet acv as a differential valve indicated be open, communication which, as shown by cording tothe direction of flow which, in turn, is determined by the setting of the valve-means VV. If the stop valve V between the ports 10-a and 11-b is established, and the motor may be propelled; rapidly if the constant displacement pump C. D. be connected throu' h the selector valve V; or at a feedrate if the variable displacement ump V. D. be connected. The direction 0 actuation, in either case will likewise be determined by the setting 0 the selector valve as to whether terminal P with terminal a a or b and H with b or a a for a feed-stroke; or terminal 3 with aa or 6 and 5 with b or ac a for a quicktraverse stroke.

The position of the valve V shown diagrammatically in the drawings indicates its position when the table right. If the valve is oscillated, terminals 3b and 5ar, will be connected and a traverse rate ensues; if the valve is next shifted axially, terminals Pb and Ha will be connected which reverses the feed connections andthe motor is driven to the left at a feed rate, etc. Inasmuch as the val means herein illustrated are representative of a conventional selector valve of the type illustrated in the above mentioned Brit ish patent, further description thereof, in the interests of clarity, be unnecessary.

In each of the diagrams; the motor feedstroke out-take line (characterized by a relatively high back-pressure) is indicated by H and may be said to embrace the portion starting from the valve means VV at H and ending at H where the automatic choke is located. This choke takes form, preferably, enerally by wh1ch,in turn, admits of modification. In its more elementary form (represented by Fig. 1) it maintains the back-pressure at a constant high value by reason of the conduit S} which connects the low constant-pressure line L with the larger chamber of the valve; the valves being represented by Hd =Ld where H and L are the potentials and d and the respective areas of the differential valve. In place of the connection a sprmg S may be employed as shown by F1 2 and 3, or conversely.

In the case of application to a milling machine, the conditions of usage generally are best met by a further refinement; to wit, the additional influence of the forward-pressure Figs. 2 and .3, is introduced by the connection P from the forward T is feeding to the line P to the chamber P of the vdifferential valve. In this case, if S be the unit pressure of the spring, and the idling pressure in thelines be represented by H then s.=H R 91) has been thought to d to substitute a small port 7 of the V. D

V to wit, V D is communicated pump which delivers oil at a selectable volumetric rate through the outlet port P into the line P which at P enters the valve means and is directed thereby as has been explained. The V. D. pump may draw its supply directly from the reservoir R but, as a matter of simplicity in piping and for other reasons, it preferably derives its supply from the oil exhausted under low-pressure by the differential valve D. This will exceed the 4 needs of the V. D. pump when the exhaust comes from the large end of the differential motor, and will be insufiicient when it comes in the piston-rod end. But if a nondifi'erential motor be used, then it will be equal in each direction of actuation. Q Of course, if no rapid traverse be required for the mechanism, then the O. D. pump and its circuit may be omitted, and the V. D. pump may draw all or some of its supply irectly from the reservoir; but it is desirable to arrange for a moderate head, at least, at the inlet port 7 of the V. D. pump because they are usually made without springs for returning the plunger and hence are not designed to operate under a negative inlet head. Hence, in any event, it is more satisfactory pump purely for makeup purposes if the larger capacity C. D. pump is not primarily needed for quick-traverse operations and ,up purposes. Such a pump, whether large or small, draws its supply directly from the reservoir R and discharges into the low-pressure line L which usually has a safety relief constant displacement pump ultimately disto the reservoir through a free after first entering the motor or through a connection from terminals 3 to 5 provided by the valve-means V V. But, to ensure a low constant-pressure available for the inlet of the V. D. pum a low fixed resistance valve 4 is arrange to choke the discharge of the C. D. pump. Between that resistance 4 and the, G. D. pump, as at 2, a communication is established with the inlet pump and this commumcation extends, as indicated by the line 8- '9 to the outlet of the differential valve D. 1

Now, byway of a further refinement of this invention, to compensate for variations in the feed-rate attributable to'such leakage charges back line F either incidentally used for make as occurs between the forward-pressure and the reservoir, it is proposed to arrange for a' high-pressure bleed into the forward-pressure line P. How'this may be done is disclosed by Fig. 3; in which B represents a small-displacement high-pressure boosterpump which draws its oil from any available source which, as a matter of convenience, ma be at some point m in communication with the low-pressure line so as to have a positive pressure on thepump inlet for the reason previously explained.

This booster-pump discharges at m into the line M which at/m, connects with an adjustable orifice O which bleeds into the forward-pressure line P. If the pressure in the line M be constant in ratio to the forwardressure in line P for all variations in the atter, and if the orifice 0 be initially adj usted to the leakage factor of the particular machine, then will the compensation remain exact for all variations in work-resistance.

This constant ratio is obtained by an auto- 'matic drainage of excess fluid by the operation of a differential valve C which, for the Egrpose of this disclosure, is illustrated as mg proportioned in a 2:1 ratio. Its tapered stem, which governs the drainage (through the line from the point m to the inlet 0 and variable outlet 0) is of one half the area of the head which is subjected to the pressure of forward-pressure line P; the communication being through the inlet 0 and the line to the point P The pressure in the line M will, accordingly always be twice the forward-pressure in the line P, and if the orifice 0 be once adjusted to equal the aggregate leakage orifices from the outlet of the V. D. pump to the reservoir, then a perfect compensation will be ensured for this type of leakage. This will suflice for most cases.

So also, for the operationof any auxiliary mechanism, a high-pressure take-oif line N other differential valve of leakage has also a retarding effect on t e may be provided.

If greater refinement required, (for leakage between forward-pres sure in line P. and the intake of the V. 1). pump) this invention pro oses. the use of an- Since this ty e feed-rate, and hence must be compensated for by a bleed-in, and since'it will in amount vary in direct proportion'to the differentials (between the forward and back-pressures) created by the variations in the work resist ance; the valve E raining such accordance therewith. The back-pressure on the V. D. pump is, in this system, constant and hence can be represented in the valve by a spring of equal unit pressure value and ar-' ranged to act in opposition to the component of the forward-pressure. As the area of the plunger head subjected tothe forwardres- 5 sure is doublev the of the stem w "ch in compensation be should be capable of asc'er- I difierentials. and operate in y (through port e is subjected to that of the maintained under a'pressure of2P-S" And, by the line W, the fluid will be available for bleeding-in at a pressure greater than the forward-pressure by an amount equal to the differential. Soto compensate for the leakage between P and L, it is only necessary to interpose in the line W an adjustable choke G for setting the rate of bleed into the forward line Paccording to' the leakage characteristic of the particular machine.

By following the principles disclosed, exact compensation for local leakage may be had between any two stations in an hydraulic system by utilizing additional valves of this type arranged in series with the 'above described valves. l

Without further analysis, the foregoing will so fully reveal the gist of this invention that others can, byap lying current knowledge, readily adapt it 1 hr various utilizations by retaining one or more of the features that,

from the-standpoint of the prior art, fairly constitute essential characteristics of either the generic or specific aspects of this invention and, therefore, such adaptations should be,

and are intended to be, comprehended within,

means maintaining the discharge from said motor under a relatively high pressure com prising a valve mechanism, having a variable orifice, adapted to respond to the combined influence of the motor discharge and pump intake pressures.

2. An hydraulic system combining a motor; a variable delivery pump arranged to receive its fluid at a relatively low pressure and to deliver same to said motor at a predetermined rate; and means maintaining the discharge from said motor under a relatively highpressure comprising a valve mechanism, having a variable orifice, adapted to respond to the combined influence of the pressures ahead of and behind the valve.

3. An hydraulic system combining a lowpressure pump; a variable-delivery pump; a conduit therebetween; a motor; a motor intake line connectible with said variable delivery pump; an out-take line from said motor to said conduit; and a high-pressure relief-valve in said out-take line for maintaining said motor under a relatively high fluid at the intake side thereof at a said variable-delivery pump; an out-take line from said motor; andan automatic relief valve for maintaining a relatively-high backpressure in said out-take line.

5. An oil-transmission system combining I a motor; anunrestricted return-conduit; a

s out-take line, said di restricted out-take line; an automatic means responsive to variations in the pressure of the controlled fluid for controlling the degree of said restriction; a source of low-pressure oil; a variable-delivery pump; valve-means for connecting said source and return-conduit with said motor to propel it rapidly and alternatively available to connect said motor with 4 said variable-delivery stricted out-take line. I v

6. An hydraulic system combining a motor; a variable-delivery pump; an in-take line from said pump to said motor; an outtake line from said motor; and a differential plunger and an escapement valve operated thereby for regulatin the out-flow in said erential plunger connected to said in-take line.

7. An hydraulic s stem combining a motor; an in-take line eading thereto; an outtake line leading therefrom; a source of fluid supply connected with the intake line; and

pump and said remeans in said out-take line for automatically from;

diminishing the back-pressure therein in accordance with increases of the forward-pressure in the in-take line.

8. An hydraulic system combining a motor; in-take and out-take lines therefor; and a differential Valve, having a variable orifice,

varying the effectiveness of said orifice thereby; to regulate the back-pressure in the out take line.

9. An hydraulic system combining a largevolume low-pressure pump; a variable-delivery pump adapted to receivefluid there a low-pressure escapement between said pumps for maintaining the oil received by said second pump at a low constant-pressure; a motor connected to receive the output from said variable-delivery pump; a motor intake line: an out-take line from said "motor; and a diflerential valve in said outtake line, said valve being connected with the in-take line and provided with an adjustable orifice capable of variation under the combined influence of the in-take and out-take pressures on said motor.

having its intake conand adapted to respond. to thecombined pressures in both lines for 10. An hydraulic system combining a movalve in said outtake line and provided with a variable orifice for regulating the out-flow,

said difl'erential valve being connected to I said in-take and out-take lines and proportioned to be more sensitive to variations in the forward than in the back-pressure in effecting variations in the resistance to flow oflered by the valve.

11. An hydraulic system combining a motor; an intake-line leading thereto; an out take line leading therefrom; means in said out-take line for automatically diminishing the back-pressure therein in a predetermined ratio to increases in the forward-pressure in the intake-line; selective means for supplyin said in take line with oil at a predetermine volumetric rate; and valve means for connecting said in-take line to drive said motor in either direction.

12. An hydraulic system combining a motor; in-take and out-take lines therefor; and a diii'erential valve in the out-take line provided with a variable orifice and having respective areas subjected to the pressures of both lines for re 'lilating the effectiveness of the valve orifice thereby to regulate the backpressure in the out-take line, the area subgecged to the forward pressurebeing relativear e. 18. hydraulic system combining a motor; a large-volume low-pressure 'pump;'a variable-delivery pump adapted to receive fluid therefrom; a low-pressure escapement between said pumps for maintainin the oil received by said second pump at a low constant-pressure; valve means adapted to connect said motor with said low-pressure pump,

or to receive the out-put from said variabledelivery pump; an out-take line from said motor; and a difl'erential valve-in said line having a variable orifice capable of variation by the combined influence of the in-take and out-take pressures on said motor; for automatically regulating the flow in said line.

14. An oil-transmission system combining a motor; a free-return conduit; a restricted out-take line; a differential valve automaticallyresponsive to variations in the pressure of the controlled fluid controlling the degree of said restriction; a source of low-pressure oil; a variable-delivery pump; valve-means for connecting said source and said freereturn conduit with said motor to propel it rapidly, and alternatively available to connect said'motor with said variable-delivery pump and said. automatically restricted outtake line.

15. An hydraulic system combining motor; a constant displacement pump; an output and free-return line; valve means selectively operable for connecting said motor,

' maintaining a pump, and/lines for rapid-propulsion; a variable-delivery pump; a motor in-take line therefrom; a motor out-take line; means relatively high back-pressure in said out-take line and permitting discharge at a relatively low-pressure into sai variable-delivery pump; a make-up connection from the aforesaid out-put line to the inlet of said variable-delivery pump; and a resistance beyond said connection in said out-put line for maintaining a relatively low constant-pressure in said connection, the firstout-take lines.

mentioned valve-means being alternatively operable to connect said motor with said variable-delivery pump through said in-take and 16. An hydraulic system combining a variable-delivery pump; a make-up pump havsaid portion to variable-delivery pump;

. out-take relatively low-pressure into said varia le-de-.

' in a portion of ing an out-put line; means for maintaining said out-put line a relatively low constant-pressure; a connection om the variable-delivery pump; a motor; an in-take line thereto from said an out-take line from said motor to said variabledelivery pump; and intervening means in said out-take line for maintaining said motor under a relatively high back-pressure.

17 An hydraulic system combining a motor; a constant displacement pump; an out put and free-return line; valve means selec tively operable for connecting said motor, pump, and lines for rapid-propulsion; a variable-delivery pump; a motor in-take line therefrom; a motor out-take line; difierential. valve means responsive to variations in pressure in portions of the system for maintaining a relatively high back-pressure in said line and permitting-dischar e at a a make-up connection from the aforesaid out-put line to the inlet of said variable-delivery pump; and a resistance beyond said connection in said out-put line for maintaining a relatively low constant-pressure in said connection, the first-mentioned valve-means being alternatively operable to connect said motor with said variable-delivery pump;

livery pump through said in-take and outtake lines.

18. An hydraulic system combining a variable-delivery pump; a make-up pump havlng an out-put line; means for maintaining n a portion of said out-put line a relatively low constant-pressure; a connection from said portion to the variable-delivery pump; amotor; an in-take line thereto from said variable-delivery pump; an out-take line from said motor to said variable-delivery pump; and a differential valve in said out-take line, res

tor; a varlable-deliverypump; an 1nlines tor;

' received by said second pump at a nsive to ressurevariations in the conv,jro ledfluid, or maintaining said motor und in-take line; and automatic means for in jecting fluid into the in-take line. to com-- pensate for leakage.

20. An hydraulic system combining a motor; an in-take line leading thereto; an outtake line leading therefrom; a source of fluid supply connected with the in-take line; and means in said out-take line for automatically diminishing the back-pressure therein in accordance with increases of the forward-pressure in the in-take line; and automatic means for injecting fluid into the in-take line to compensate for leakage. v

21. An hydraulic system combining a motor; in-take and out-take lines therefor; and a differential valve in the out-take line acting under the combined pressures in both to regulate the flow and thereby control the back-pressure in the out-take line; and automatic means for injecting fluid into the in-take line to compensate for leakage.

22. An hydraulic system combining a moa variable-delivery pump; an in-take line'from said pump to said motor; an outtake line from said motor; and a differential valve provided with a variable openin said out-take line for regulating the outow, said differential valve being connected to said in-take line and proportioned to be more sensitive to variations in the forward than in the back-pressure in varying the eifectiveness of the valve 0 ning; and automatic means for injecting uid into the in-take-line to compensate for leakage.

23. An hydraulic system combining a mo tor; a large-volume low-pressure pump; a variable-delivery pump adapted to receive fluid therefrom; a low-pressure escapement between said pumps for maintaining the oil ow constunt-pressure; valve means adapted to con- 7 nect said motor with said low-pressure pump, or to receive the out-put from said variabledeliveryump; a motor intake line; an outtake line rom said motor; a differential valve in said out-take line, said valve being connected with said in-take and out-take lines and provided with an orifice capable of variation by and in accordance with variations in the combined influence of the in-take and out-take pressures on said motor and automatic means for injecting fluid into the in-take line to compensa'te for leaka 24. An hydraulic system combining a motor; a constant displacement pump; an output and free-return line; valve means selectively operable for connecting said motor, pump and lines for rapid-propulsion; a variableeli'very pump; a motor in-take line therefrom; a motor out-take line; means maintaining a relatively high back-pressure in said out-take line and permitting discharge at a relatively low-pressure into said variable-J delivery pump; a make-up connection from the aforesaid out-put line to the inlet of said variabledelivery pump; and a resistance beyond said connection in said out-put line for maintaining a relatively low constant-pressure in said connection, the first-mentioned. valve-means being alternatively operable to connect said motor with said variable-delivery pump through said in-take and outtake lines; and automatic means for injecting fluid into the in-take line to compensate for leakage. I 1

25. An hydraulic system combining a variable-delivery pump; a make-up pump having an out-put'line; means for maintaining ina' portion of said out-put line'a relatively low constant-pressure; a connection from said portion to the variable-delivery pump a, mo tor; an in-take line thereto from said'variabledelivery pump; an out-take line from said motor to said variable-delivery pump; and

intervening means in said out-take line for maintaining said motor under a relatively high back-pressure; and automatic means for injecting fluid into the in-take line to com pensate for leakage.

26. An hydraulic system combining a variable-delivery pump; a make-up pump having an out-put line; means for maintaining in a portion of said out-put line a relatively low constant-pressure; a connection from said portion to the variable-delivery pump; a motor; an in-take line thereto from said variable-delivery pump; an out-take line from said motor to said variabledelivery pump; and a differential valve, provided with a variable orifice, in said out-take line for maintaming said motor under a relatively high bac -.pressure; said valve respondin to variations in pressure ofthe controlle fluid to regulate the effectiveness of the valve orifice; and automatic means for injectin fluid into the in-take line to compensate for eakage. In witness whereof, I have hereunto sul scribed my name.

BERNARD SASSEN. 

